1. Field
One embodiment of the invention relates to a main apparatus that is used, for example, for an internet protocol (IP) telephone system, and a control signal distribution regulation method used in the main apparatus.
2. Description of the Related Art
In recent years, an IP telephone system, in which an image and voice are exchanged interactively in real time through an IP network, has started to become widespread. In this IP telephone system, not to mention that each main apparatus connected to an IP network can carry out inter-extension communication and call incoming and outgoing using an external line, extension communication and call incoming and outgoing using an external line between main apparatuses through an IP network can be carried out.
With respect to the main apparatus, when a user using a terminal A presses a “Line” key to carry out call origination operation, a NOTIFY message is transmitted to a terminal B and a terminal C in which the same “Line” key is registered, and light emitting diode (LED) control or liquid crystal display (LCD) control of the “Line” key is carried out depending on a call state. Also, for multi-appearance that distributes an incoming call addressed to a group, in which the same “Line” key is registered, to terminals in the group, the NOTIFY message is transmitted, and LED control or the LCD control of the “Line” key is carried out depending on a call state.
In the above IP telephone system, the main apparatus is shared by a number of terminals, personal computers, and the like on an IP network. Therefore, the main apparatus is well predicted to be in a congestion state. When the main apparatus is in a congestion state, influences, such as loss of real time, are provided to services, such as communication connection between terminals corresponding to call incoming and outgoing.
In view of the above, a conventional communication system proposes a method, in which an SIP server monitors congestion, and when there is regulation during congestion, all incoming and outgoing calls are regulated, except for a call for which priority is registered, so that a load of a system is reduced (for example, Jpn. Pat. Appln. Publication No. 2007-184798).
There has been strong demand for a method that can efficiently process at least services relating to call incoming and outgoing even when the main apparatus is in a congestion state, in the IP telephone system.